The 90% Shoulder: Why Your Sports Injury Started Before the Impact
It always happens the same way.
An athlete walks into my clinic and tells me about the exact moment their injury happened.
"I was playing water polo last week and someone hit my elbow during a throw. My shoulder's been killing me ever since."
Or: "I've been lifting for years with no problems. Then I did one set of overhead press and my shoulder just gave out."
Or: "I was fine all season, then on one normal training run, my knee started hurting and hasn't stopped."
They want to know: Why did THIS moment cause so much pain?
Let me be honest with you right back: that hit didn't cause your injury. It exposed a problem that was already there.
The 90% Principle
Think of it like this: You haven't worked out in a year. Then one day you decide to crush a full CrossFit workout—everything at max intensity.
The next day, you're destroyed. Sore everywhere. Can barely move.
Did that one workout "cause" your soreness?
Well, yes and no. The workout triggered the response. But the real issue is that your system wasn't prepared to handle that load. If you'd been training consistently, that same workout would've just been Tuesday.
Your shoulder injury works the same way.
Most athletes are walking around with compensation patterns running at 90% capacity. Everything FEELS fine. Performance is good. No pain. You're training hard, competing well, crushing your workouts.
But underneath, your body is working overtime to keep you moving.
Here's what's actually happening:
Weeks 1-12: The Slow Build
A muscle gets weak (maybe your shoulder blade stabilizers aren't firing properly)
Another muscle gets tight to compensate (your chest starts pulling your shoulder forward)
Other muscles work harder to pick up the slack (your rotator cuff is grinding to stabilize what those weak stabilizers should be handling)
You feel… nothing. Maybe some tightness after workouts. Maybe you "sleep on it wrong" once in a while.
Week 13: You're at 90%
Your system is barely keeping up
Every throw, every lift, every movement is maxing out your compensation capacity
But you don't know it because there's no pain
Week 14: The "Injury"
One bad throw
One awkward landing
Someone bumps into you
Your system gets pushed to 110%
Something has to give
The tissue fails.
And everyone—including you—blames the hit, the throw, the landing.
But that was just the final straw. Your body was already at 90%. That moment just pushed it over.
The Real Story: A Water Polo Player's Journey
Let me tell you about a patient It's a perfect example of how these "sudden" injuries actually develop.
12 months ago: He had shoulder bursitis. Got acupuncture treatment, inflammation resolved over the summer. He felt great.
The following year: Someone hit his elbow during a throw. Immediate "pop" in his shoulder. Sharp pain. Couldn't throw hard anymore.
He walked in asking: "Why did that one hit cause so much damage?"
Here's what I found when I assessed him:
Both shoulder blade muscles (serratus anterior) were weak—not firing properly
His right hip stabilizer (glute med) wasn't activating
His chest muscle (pec minor) was pulling his shoulder forward
His back shoulder muscles were working overtime trying to compensate for everything else
I know that might sound like I'm splitting hairs, but this pattern didn't happen in 2 weeks. This took MONTHS to develop.
That bursitis last year? That was the first warning sign. His shoulder was already compensating, already running at 85%. The bursitis was his body saying "pay attention to me here"—that signal telling him something's wrong.
He got treatment. The inflammation went away. He felt better.
But the underlying weakness and tightness? Never addressed.
Fast forward to October. He's back to playing hard. His system is now running at 90%.
Then someone hits his elbow during a throw.
Pop.
That hit didn't create the problem. It exposed it.
Why This Matters: Two Different Approaches
The Symptom-Chasing Approach (What Most Athletes Do):
Ice the shoulder
Take ibuprofen
Rest until the pain goes away
"It feels better now!"
Return to sport
Re-injure within weeks or months
Why this fails: You treated the inflammation—the screaming muscle that's in pain right now. But the sleeping muscles that CAUSED the imbalance? Still asleep. The tightness that pulled everything out of position? Still tight.
You addressed one side of the equation. That's not enough.
The Root Cause Approach:
Treat the acute inflammation (yes, we need to calm down that screaming muscle)
Identify the underlying dysfunction through comprehensive assessment
Address BOTH sides of the imbalance—we need to wake up those sleeping muscles AND release what's too tight
Rebuild the system to handle the demands of your sport
Return to sport with the foundation actually fixed
This is what we call the yin and yang approach in Eastern medicine. We're not just treating one side of the problem—we're addressing both the screaming muscle and the sleeping one simultaneously.
The Missing Piece: Exercise Prescription
Here's what I told my water polo patient, and I'm going to sound like a broken record about this:
"The acupuncture I'm giving you will reduce the inflammation and help the tissues heal. I'm using motor points to essentially jumpstart those weak, underactive muscles—like putting jumper cables on a dead car battery. The manual therapy will release the tight muscles pulling your shoulder out of position.
But if we don't strengthen those weak stabilizers through corrective exercises and fix how your body moves, you'll be back here in 6 months with the same problem—or worse."
I gave him three exercises:
Wall slides - to rebuild his weak shoulder blade muscles
Clamshells - to stabilize his weak hip
Founder (a Foundation Training exercise) - to integrate his whole posterior chain
Why these three specific exercises?
His shoulder pain wasn't actually a shoulder problem. It was a kinetic chain problem. When your hip muscles aren't doing their job properly, muscles higher up the chain have to pick up the slack.
His weak hip meant he couldn't generate power from the ground during his throw. His weak shoulder blade muscles meant his shoulder was unstable through the throwing motion. His tight chest was pulling everything forward, making the whole system work even harder.
The exercises address the root cause, not just the symptom.
Think of it like this: Acupuncture with motor points jumpstarts those sleeping muscles and calms down the screaming ones. But exercise prescription teaches them how to fire properly again, how to work together as a system.
You need both. Understanding the process makes all the difference.
Warning Signs You're Running at 90%
How do you know if you're at 90% capacity, one bad movement away from injury?
Physical Signals:
Tightness that won't go away despite stretching and rolling out
Feeling "unstable" or "loose" during movements
Compensating or adjusting your technique without realizing it
One side feels different than the other
Occasional pain that comes and goes for no clear reason
Previous minor injuries in the same area (bursitis, tendinitis, those "tweaks" you brushed off)
Performance Signals:
Decreased performance despite same training volume
Movements that used to feel smooth now feel "off"
Fatigue in weird places (neck tight when throwing, low back sore after swimming)
Needing more warm-up time to feel "loose"
The Big One:
You had an injury before that "got better" but you never did actual rehab exercises—you just waited until it didn't hurt anymore
If you're checking off three or more of these, your body is trying to tell you something. That signal is saying "this area needs help" or "please focus your healing attention here."
Don't ignore it.
What To Do If You're at 90% (Or Already Injured)
If you're currently injured:
Don't wait and see. I get it—you're hoping it'll just resolve on its own. Sometimes inflammation does calm down. But if the underlying dysfunction is still there, you're just resetting to 90% and waiting for the next "sudden" injury.
Get assessed by someone who looks at the WHOLE system, not just where it hurts. Each case is different, so we need to focus on you and your condition specifically.
Ask about underlying dysfunction. If a practitioner only wants to treat the pain site without assessing what's weak, what's tight, and what's compensating, that's a red flag.
Commit to the exercise prescription. Manual therapy—acupuncture, massage, adjustments—helps healing and feels great. But exercises fix the cause. You need both sides of that equation.
If you're NOT injured but see warning signs:
Get a movement assessment. Find your weak links BEFORE they become injury sites.
Add corrective exercises to your routine. Even 10 minutes three times per week of targeted exercises can prevent months of rehab later. What felt challenging at first becomes manageable—just like building training tolerance.
Listen to what your body is telling you. If your neck is always tight, your hip flexors are always cranky, or you "feel better on one side"—these are messages. Your body is essentially saying "pay attention to me here."
The Bottom Line
That "sudden" injury wasn't sudden.
It was weeks or months of compensation, weakness, and tightness building to a breaking point. The impact, the throw, the lift—that was just the final 10% that pushed your system beyond capacity.
If you only treat the acute injury, you'll be back at 90% soon, waiting for the next "sudden" injury.
If you address the root cause—the weakness, the tightness, the compensation pattern—you'll build a system that can handle more than 100% without breaking.
My water polo player? We're two weeks into treatment. His pain has decreased significantly. His shoulder blade muscles are firing again. His hip is stabilizing. His shoulder isn't being pulled forward anymore.
More importantly, he understands WHY he got injured and WHAT he needs to do to prevent it from happening again.
That's the difference between temporary relief and long-term recovery.
The whole goal is for you to keep doing what you love. Your body wants to heal and perform—sometimes it just needs help addressing both sides of the equation.
Ready to Discover Your Pattern?
If you're dealing with a "sudden" injury that doesn't make sense, recurring issues in the same area, or that feeling that something's "not right" even though nothing hurts yet—the problem might not be at the injury site.
It might be the compensation pattern that's been building for months. And that pattern is unique to your body, your training history, your specific sport.
Understanding YOUR specific pattern—that's where assessment becomes crucial.
What happens next is your choice.
You can keep managing symptoms as they pop up. Or you can work with someone who sees these patterns in athletes every day and knows how to address both the screaming muscle and the sleeping one.
Located in San Diego? I offer a free 20-minute consultation where we can talk about what you're dealing with and whether this approach makes sense for your situation. No pressure, no sales pitch—just an honest conversation about your body and what it needs.
Schedule Your Free Consultation
Questions about the 90% principle or how root cause treatment works? Drop them in the comments below.
About Mike Cohen: Licensed acupuncturist specializing in sports medicine at Acupuncture Athlete in San Diego. Former rugby player and current marathon runner who bridges Eastern wisdom with Western science to help athletes understand their bodies and get back to doing what they love.